Precision Laser Studies of Basic Atoms and Nuclei

与围绕太阳旋转的行星不同，原子内部围绕原子核旋转的电子不允许在任意距离上这样做。量子理论规定，与原子核之间的平均距离只允许有非常特定的距离。这种限制产生了原子在受到激光束照射时所反应的特定颜色的光。通过精确调节激光，人们可以找到与轨道电子共振的特定颜色，从而了解原子内部结构的复杂细节。虽然大多数原子都有很多电子，使得理解复杂的轨道模式的任务相对困难，但氢和氦分别只有一个和两个电子，因此可以进行非常精确的理论预测。通过将这些非常精确的预测与类似的精确测量相比较，人们可以检验“量子电动力学”理论（关于光、原子和我们周围大多数普通世界的基本理论）是否真的正确，或者只是大致正确。得到这笔拨款支持的小组计划开发和部署激光源和技术，以改进上述量子理论的测试。如果这个理论在新的精度水平上被证明是正确的，那么实验结果就可以用来确定氢和氦原子核的大小。将这些大小与核物理学中已知或预测的大小进行比较，将为对这些简单原子核的科学理解提供检验。通过这种方式，这些实验弥合了原子和原子核之间的差距，并测试了长度尺度相差一万倍的两种物理体系的一致性。激光光源和光学技术在科学、技术和经济中无处不在，因此在这一领域培养学生提供了宝贵的专业知识，并有可能开发出广泛应用的重要激光光源和光学技术。本研究发展了激光技术和精密激光技术。它应用于氦精细结构的研究和氢、氦核尺寸的精确测定。光学方法包括对稳定的半导体激光器进行高速电光调制，在激光器上产生微波可调谐的频带。这些边带可以用来驱动和确定氦3和氦4中的2S - 2P三重态以及氢及其同位素中的1S-2S的跃迁频率。仔细研究了激光与氢和氦原子相互作用的物理性质，以获得所研究原子跃迁的无扰动频率。结果将获得足够的精度，以提供重要的理论比较。这些包括(1)氦原子（最简单的多电子原子）中电子-电子相互作用的原子理论和计算，以及(2)预测观察到的少核子核大小的核相互作用和计算。特别是，这些实验结果中的同位素变化可以确定氦-3和氚的电荷半径，并与少核子理论的预测和核力的基本描述进行比较。

Unlike the planets orbiting the sun, the electrons that whorl around the nucleus inside atoms are not allowed to do so at arbitrary distances. Quantum theory prescribes that only very specific average distances from the nucleus are allowed. This limitation gives rise to the specific colors of light that atoms respond to when hit with a laser beam. By tuning the laser precisely, one can find the specific colors that are in resonance with the orbiting electron, and thereby learn about the intricate details of the internal structure of the atom. While most atoms have many electrons, making the task of understanding the complicated pattern of orbits relatively difficult, hydrogen and helium have only one and two electrons, respectively, and hence are amenable to very precise theoretical prediction. By comparing these very precise predictions to similarly precise measurements, one can test whether or not the theory of "quantum electrodynamics" (the fundamental theory of light, atoms, and most of the rest of the ordinary world around us) is really correct, or only approximately so. The group supported by this grant plans to develop and deploy the laser sources and techniques that will allow improved tests of the quantum theory described above. If the theory is found to be correct at the new level of accuracy, the results of the experiments can then be used to determine the size of the nucleus in hydrogen and helium. A comparison of these sizes with what is known or predicted in nuclear physics will then provide a test of the scientific understanding of these simple nuclei. In this way, these experiments bridge the gap between the atom and the nucleus, and test the consistency of two regimes of physics which differ in length scale by a factor of 10,000. Laser sources and optical techniques are ubiquitous in science, technology and the economy, so training of students in this area provides valuable expertise, and has the potential to develop generally important laser sources and optical techniques for a wide range of applications. This research develops laser technology and precision laser techniques. It applies them to the study of helium fine structure and the precise determination of hydrogen and helium nuclear sizes. Optical methods are developed which involve high-speed electro-optic modulation of a stabilized semiconductor laser, creating microwave tunable frequency side bands on the laser. These side bands can then be used to drive and determine the transitions frequencies of the triplet 2S - 2P in helium 3 and 4, and 1S-2S in hydrogen and its isotopes. The physics of the laser interaction with hydrogen and helium atoms is carefully studied to obtain the unperturbed frequencies of studied atomic transitions. Results will be obtained with sufficient precision to provide important comparisons with theory. These include (1) the atomic theory and computation of electron-electron interactions in helium, the simplest multi-electron atom, and (2) the nuclear interactions and computations that predict the observed size of few-nucleon nuclei. In particular, isotopic shifts in these experimental results allow the charge radii of helium-3 and tritium to be determined and compared to predictions of few-nucleon theory and the underlying description of the nuclear force.